1. Field
The disclosed and claimed concept relates generally to electrical distribution equipment and, more particularly, to an electric surge protection device for use in an electrical enclosure.
2. Related Art
Electrical distribution equipment is generally well understood in the relevant art. Electrical distribution equipment includes, by way of example, load centers, circuit breaker enclosures, circuit breakers, wires, and other such equipment. While such equipment has been generally effective for its intended purposes, it has not been without limitation.
It is understood that an electrical supply can suffer from voltage fluctuations and occasional voltage surges or spikes. Most electrical equipment that is connected with a source of electrical power is designed to accommodate voltage fluctuations but is not typically configured to withstand a voltage surge beyond a nominal voltage increase.
It thus has been known to provide surge protection devices that include structures such as varistors and the like that are configured to shunt current to a ground or a neutral conductor when excessive voltage is encountered. A varistor has a resistance that changes as a function of the voltage that is experienced. At or below a predetermined voltage, the resistance of the varistor is very high. However, the resistance of the varistor drops rapidly in response to voltage above a predetermined threshold. As such, varistors are typically connected between a line conductor and a ground or a neutral conductor and conduct very little current to the ground or neutral conductor when normal voltages, i.e., voltages within a predetermined voltage range, are experienced. However, when the voltage surges outside the predetermined range, the varistors experience reduced resistance and thus shunt electrical power from the voltage surge to the ground or neutral conductor, thereby protecting from destruction a piece of electrical equipment that is connected with the same circuit. One common type of varistor is the metal-oxide varistor (MOV), although other types of varistors are usable in surge protection applications.
It is also known, however, that a varistor is typically designed to shunt significant power for only a short duration of time and typically does not have the capacity to shunt excess power in a sustained fashion over an extended period of time. Depending upon the voltage surge, one or more varistors can experience catastrophic failure, which can result in the generation of high pressures or temperatures or both being generated by the failing varistors. It thus would be desirable to provide an improved electrical surge protection device that provides improved performance.